New diarylmethane derivatives, their manufacture and application



United States Patent NEW DIARYLIVIETHANE DERIVATIVES THEIR MANUFACTUREAND APPLICATION Arthur Lambert and Boris Nicholas Lyland, Manchester,England, assignors to Imperial Chemical Industries Limited, London,England, a corporation of Great Britain No Drawing. Application December19, 1955 Serial No. 553,706

Claims priority, application Great Britain December 24, 1954 4 Claims..(Cl. 260--8 l0) This invention relates to new chemical compounds namelybis-(2-hydroxy 3 a alkylcycloal kyl 5 ethylantiagers for natural andsynthetic rubbers, polyethylene,

and for those oils, fats and waxes which tend to deteriorate in thepresence of oxygen and valuable intermediates for the manufacture ofother compounds, including other antiagers, e.g. metal salts of theabovenew compounds. The new compounds are, according to one process ofthe invention, manufactured intwo stages. The first stage consists ofcombining, in the presence of an acid condensing agent, I molecularproportion of p-ethylphenol with 1 molecular proportion of ana-alkylcyclopentene, methyl a alkylcyclopentene, a alkylcyclohexene ormethyla-alkylcyclohexene, in which the alkyl substituent has not morethan 4 carbonatoms. In the second stage, two molecular proportions ofthe p-ethylphenol derivative, i.e. 2-a-alkylcyc1oalkyl-4-ethylphenol,which is obtained in the first stage, are condensed with one molecularproportion of formaldehyde or of a substance yielding formaldehyde, inthe presence of an acid condensing same or a different p-ethylphenolderivative in the presence of an acid condensingagent.

As a further alternative for the second stage a chloromethyl substituentis introduced in to the p ethylphenol derivative by reacting it with onemolecular proportion of formaldehyde in the presence of'anhydroushydrogen chloride and the resulting chloromethyl derivative is thencondensed with a second molecular proportion'of the same or a differentp-ethylphenol. derivative.

These alternatives for the second stage provide convenient ways ofmanufacturing such of the new compounds of this invention as are notsymmetrical, i.e.

The antioxidants are employed in the manufacture of rubber articlesaccording to the usual methods. Thus they may for example be mixed withthe rubber along with vulcanising and other ingredients and theresulting mixes then cured by heat treatment, or they may be mixed alongwith other compounding ingredients and the mixture vulcanised bytreatment with sulphur monochloride in the cold. The antioxidants areeffective in proportions of from A1 to 2 percent of the weight of therubber.

The synthetic rubbers which may be used include for example polymers ofbutadiene-l :3-isobutene and 2- chlorobutadiene-1z3- and copolymers ofeither of these compounds with acrylonitrile, styrene,methylmethacrylate and other well known polymerisable compounds whichare used in the manufacture of these rubbers.

The invention also relates to the application of the new compoundsasantioxidants for natural and synthetic rubber.

The following examples in which the parts are by Weight illustrate butdo not limit the invention.

Example 1 p-Ethylphenol (26 parts) and sulphuric acid (98% :0.7 part)are mixed at 50 'C., and l-methylcyclohexene (20.5 parts) is addedslowly with stirring at 35-45 C. After the addition, the mixture isstirred for 18 hours and is then heated with aqueous sodium hydroxide(23%:42 parts) at IOU- C. for /2 hour. The mixture is diluted with waterand the crude condensate is isolated by extraction with benzene. Bydistillation of the extract, 2-a-methylcyclohexyl-4-ethylphenol isobtained, B.P. 178-l90 C./15 mm.

2-a-methylcyclohexyl-4-ethylphenol (20 parts) is stirred withformaldehyde (37%:4.2 parts) and hydrochloric acid (35%:1.68 part) at65-75" C. for 3 hours. The product is taken up in benzene, washed withaqueous sodium bicarbonate solution and with water. On distillation ofthe benzene solution bis-(2-hydroxy-3-a-methylacyclohexyl-S-ethylphenyl)-methane is obtained, B.P. 200- 240 C./ 0.2mm., melting point after crystallisation from petroleum ether (B.P.40-60 C.) 84-865" C.

Example 2 Working by methods analogous to that of the above example, butusing homologues of the starting materials of that example, or othersimilar starting materials in accordance with the invention, there maybe obtained other antioxidants.

The substitution of a-n-butylcyclohexene for a-rnethylcyclohexene yieldsbis-(2-hydroxy-3a-n-butylcyclohexyl- S-ethylphenyl) -methane.

Similarly the substitution of u-methylcyclopentene fora-methylcyclohexene gives bis (2hydroxy-3-a-methylcyclopentyl-S-ethylphenyl)-methane. Also thesubstitution of the a-methylcyclohexene by oi'y-dimethylcyclohexene(made by dehydrating 1:4-dimethylcyclohexanol) and by u-ethylcyclohexeneyield bis-(2-hydroxy-3-wy-dimethylcyclohexyl-S-ethylphenyl)-methane andbis-(Z-hydroxy-3-a-ethylcyclohexyl-5 4 ethylphenyl) methanerespectively.

Example 3 2-a-methylcyclohexyl-4-ethylphenol is added to an aqueoussolution of formaldehyde and potassium hydroxide, the three compoundsbeing in equimolecular proportions. Methanol is added until a clearsolution is obtained and the solution left overnight. The mixture isthen neutralised with acid. The2-hydroxy-3-amethylcyclohexyl-S-ethylbenzyl alcohol which separates isthen stirred for several hours with an equimolecular proportion of2-u-methylcyclohexyl-4-ethylphenol in petroleum ether to which a littleconcentrated hydrochloric 3- The solid bis-(2-hydroxy-3-asepaacid hasbeen added. methylcyclohexyl-S-ethylphenyl)methane which rates isfiltered 01f.

Example4 The 2-hydroxy-3-a-rnethylcyclohexyl-S-ethylbenzyl alcohol whichis obtained in Example 3 is converted to the corresponding benzylchloride by treating a solution of it in ether with concentratedhydrochloric acid at a temperature below 5 C. Equimolecular proportionsof 2-a-methylcyclohexyl-4-ethylphenol and the benzyl chloride derivativeare then interacted in the cold in an inert medium. The product is thesame as that of Example 3.

I Example5 Vulcanisable rubber stocks of the following compositions wereprepared by the usual process of mixing, using bis-(2-hydroxy-3-amethylcyclohexyl 5 ethylphenyl)- methane as antioxidant and also usingno antioxidant.

Parts Mix Pele crepe natural rubber 100 100 Zine oxide 10 Blane fixe 7575 Stearic acid. 1 1 Sulphur 3 3 Diphenylguanidine 0. 5 0. 5Bis-(2-hydroxy-3-u-methylcyclohexyl- 6 ethylphenyi)- methane 1 Sheets ofeach mix were cured for 75 minutes at 141 C. and ageing tests carriedout on the vulcanisates.

Example 6 To show the non-staining properties of the antioxidants,vulcanisable rubber stocks of the following compositions were preparedby the usual process of mixing, us-

ing bis-(2-hydr0xy-3-a-methylcyclohexyl-S-ethylphenyl)- methane and alsono antioxidant.

Mix A B Pale crepe natural rubber 100 100 Zinc oxide 10 10 Blane fixe 7575 Stearic acid 1 1 Titanium dioxide. 10 Zinc dlethyldithiocarbamate 0.375 0.375 Bis-(2-hydroxy-3-a-methylcyclohexyl-5-ethy1phenyl)- methane 1A sheet of each mix was cured for 12 minutes at 125 C. Samples of thevulcanised sheets were exposed outdoors with the following results:

' Mix A Mix B Exposed outdoors for 1 week Equal to blank test. Very palecream. Exposed outdoors for 2 weeks rin Pale cream. Exposed outdoors for4 weeks do Do.

The above results show that the antioxidant does not cause any stainingat all.

Example 7 As an illustration of the use of the antioxidants in syntheticrubbers the following mix was made up:

Cure was eflected at 153 C. for 30 minutes.

Example 8 Rubber films were prepared by drying on glass plates from thefollowing mixes:

Parts 60% natural rubber latex 167 20% aqueous solution of cetylalcohol-ethylene oxide condensation product 1.0

50% aqueous dispersion of sulphur 2.0

50% aqueous dispersion of zinc oxide 3.0

50% aqueous dispersion of zinc diethyl dithiocarbamate 2.0 20% aqueousdispersion of the antioxidant of Example 1 5.0

The films were vulcanized for 30 minutes in air at C.

What we claim is:

1. A composition comprising an oxygen-susceptible natural rubber havingincorporated therein at least one bis (2 hydroxy 3 a alkylcycloalkyl 5ethylphenyl)-methane in which the cycloalkyl groups are selected fromthe class consisting of cyclopentyl, methylcyclopentyl, cyclohexyl andmethylcyclohexyl and the alkyl substituent has not more than 4 carbonatoms and is attached to the a-carbon atom of the cycloalkyl group.

2. The composition of claim 1, wherein said methane is bis(2-hydroxy-3-a-methylcyclohexyl-S-ethylphenyl)- methane.

3. The composition of claim 1, wherein said methane is his(2-hydroxy-3-a-methylcyclopentyl-S-ethylphenyl)- methane.

4. The composition of claim 1, wherein the proportion of btlljieantioxidant is A to 2 percent of the weight of said ru er.

References Cited in the file of this patent UNITED STATES PATENTS .11..Lil

1. A COMPOSITION COMPRISING AN OXYGEN-SUSCEPTIBLE NATURAL RUBBER HAVINGINCORPORATED THEREIN AT LEAST ONE BIS -(2- HYDROXY -3 - A -ALKYCYCLOALKYL -5 ETHYLPHENYL)-METHANE IN WHICH THE CYCLOALKY GROUPS ARESELECTED FROM THE CLASS CONSISTING OF CYCLOPENTYL, METHYLCYCLOPENTYL,CYCLOHEXYL SND METHYLCYCLOHEXY AND THE ALKYL SUBSTITUENT HAS NOT MORETHAN 4 CARBON ATOMS AND IS ATTACHED TO THE A-CARBON ATOM OF THECYCLOALKYL GROUP.